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Workers are back cutting into the concrete seal plugging the Pike River Mine drift after the leaky tubes that delayed the long-awaited re-entry were replaced.
Expert miners were due to enter the West Coast mine on May 3 to start an operation trying to recover the 29 men killed during the disaster on November 19, 2010.
The Pike River Recovery Agency (PRRA) had been working for months to purge methane and oxygen from the mine by pumping in nitrogen through pipes before they headed underground.
But the day before they were due to go in, they got an ‘‘unknown reading of oxygen’’ from a borehole 2.3km into the mine’s drift, where the roof collapsed in the 2010 explosions.
The oxygen had the potential for a ‘‘spontaneous combustion event’’.
‘‘Integrity testing has been completed on all the monitoring tubes that check the mine’s atmosphere,’’ PRRA chief operating officer Dinghy Pattinson said yesterday.
‘‘The concrete cutting is under way, along with other preparations for re-entry.’’